Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$194.30	10.675%	$215.0415	$215.04	$215.05	$215.00
Purchase #2	$192.66	13.111%	$217.9197	$217.92	$217.90	$217.90
Purchase #3	$55.82	6.585%	$59.4957	$59.50	$59.50	$59.50
Purchase #4	$232.44	9.567%	$254.6775	$254.68	$254.70	$254.70
Purchase #5	$203.36	10.843%	$225.4103	$225.41	$225.40	$225.40
Purchase #6	$76.62	8.502%	$83.1342	$83.13	$83.15	$83.10
Purchase #7	$35.69	4.603%	$37.3328	$37.33	$37.35	$37.30
7 purchase totals =	$990.89		$1,093.0117	$1,093.01	$1,093.05	$1,092.90